Agitation of viscous Newtonian and non‐Newtonian fluids

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Abstract
Viscous fluids are frequently agitated by multiple impellers and in vessels only slightly larger than the impeller. This paper presents data for both Newtonian and non‐Newtonian fluids agitated under such conditions. The large decreases in power requirements (at a given level of mixing rate in the non‐Newtonian system) which are possible by use of low tank diameter, impeller diameter ratios and/or two impellers, have been quantitatively studied.The types of impellers used in the non‐Newtonian work and the ranges of conditions over which power requirement correlations were developed are summarized as follows: D T/D n NRe Marine propeller 0.42‐1.0 1.4 ‐4.8 0.16‐1.0 0.67‐1320 Fan turbine 0.33‐0.67 1.3 ‐3.0 0.21‐1.4 6.6 ‐160 Flat‐Bladed turbine: one impeller 0.17‐0.67 1.3 ‐5.5 0.20‐1.5 2.0 ‐1800 two impellers per shaft 0.33‐1.00 1.023‐3.5 0.14‐1.00 0.15‐620 The results generally confirm an approach developed earlier, for the broader ranges of variables listed above. For the non‐Newtonian fluids of primary interest in this study, that is purely viscous materials having flow behavior indexes of less than unity (pseudoplastics, Bingham plastics), the prediction of power requirements has been developed to nearly the same level of perfection as for Newtonian fluids.

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